How to make a (photorealistic) material similar to tomato placenta and inner circle similar to this?
Hmmmm, as far as I understand, 


the real thing does not have a solid 1/0 boundary between the liquid and the solid part 
all surfaces have a lot of microbumps.


So what I can think of here is that you can try taking two different levels of noise textures, and using the one with larger scale value for the solid part and the one with the smaller scale for the gooey/liquid part of the tomato. 

Also, try blending in the borders between the two, make it so that the boundary of hard part is more like a slope like the ocean shore rather than a straight-up vertical fall like the well. 

And yeah, that's really it, the shine added by the correct displacement map would do most of the heavy lifting. Ofcourse you can do this manually with a fractal subdivision if you want.